Fix driver headers
Improve tests and adjust to new structure
P9221R driver updated to the new file structure
major structure overhaul:- Drivers are no longer separated in include/ and source/ folders, but a single drivers/ folder.- There is no Makefile anymore. Software, which uses the drivers has to set the according paths individually.- (De)Activation of drivers is no longer done via the alldconf.h file, but via Makefiles.